Added Remember Me feature

This is a new feature to add remember me feature in login view.

Here's the change log:

 - In class ```Authenticator``` I've changed ```toCookie``` method signature to accept a new argument which is ```rememberCookie``` as boolean
 - I've rewrote the structure of the login form to accept the ```LoginInfo``` object instead of accepting ```tuple(String, String)```
 - Add a new class ```case class LoginInfo(username: String, password: String, remember: Option[Boolean])``` to be used in the new form ```loginFormWithoutRemember``` instead of accepting two strings as username and password, so we pass the remember me option along side with the credentials
 - Added ```lazy val withRememberMe = current.configuration.getBoolean(RememberMe).getOrElse(false)```
 - Modify the view to add remember me checkbox at ```/views/provider.scala.html```